1. Field of the Invention
This invention relates to a rotary nozzle, and more particularly to a molten steel leakage prevention device suitable for a rotary nozzle.
2. Description of the Prior Art
Rotary nozzle systems have been used widely with ladles for receiving the molten steel tapped from a converter to transport or pour the molten steel into molds, tundishes for receiving the molten steel from a ladle to pour the molten steel into molds and the like. In particular, the door type rotary nozzle in which can be pivoted so as to open by hinges of a rotor containing a slide plate brick, has been widely used due to its many advantages, i.e., the bottom plate brick and the slide plate brick can be exposed to permit the confirmation of any damages on the brick surfaces by the naked eye, that there is no need to prepare any standby set for replacing or repairing the bricks, that the operation is easy and so on.
In the door type rotary nozzle, the door is mounted pivotably at the base member fixing a bottom of a ladle by hinges with which the door is opened and closed. The door is required for safety control in that the bottom plate brick and the sliding plate brick have to be tightly sealed to each other to prevent molten steel leakage and air entrance during the closed condition. A secure locking system must guarantee the door does not open during operation.
FIG. 4 shows an example of the rotary nozzle. In FIG. 4, a base member (2) is fixed with bolts on a vessel (1) of a ladle or tundishes, and a bottom plate brick (3) is mounted on the base member (2). A top nozzle (5) penetrates the hole through the vessel (1) and the base member (2) of the bottom ladle and is met with the nozzle hole (4) of the bottom plate brick (3). An annular support frame (door) (6) is mounted by rotating it on the base member (2) with a hinge (7). A rotor (8) is housed in the annular support frame (6) and mounted by rotating it onto the movable support member (13) via a ball bearing (9). The rotor (8) also has a gear (10) on the outer periphery engaged with another gear (not shown) coupled to a driving source, and houses a slide plate brick (11) facing the bottom plate brick (3) in the upper portion. A collector nozzle (14) is coupled to the slide plate brick (11). Both the nozzle (4) of the bottom plate brick (3) and the nozzle bore (12) of the slide plate brick (11), are formed so as to shift by distance d from the center axis 0--0 of the bricks (3) and the nozzle bore (11) (see FIG. 5(a)). A spring seat (15) faces the movable support member (13) in the annular support frame (6), and is close mounted along the periphery of the rotor (8) (FIG. 5(a)). A coil spring (16) is placed between the movable support member (13) and the spring seat (15).
FIG. 5(b) shows a use of the brick (11a) in polygon surrounded by many coil springs (16) which the applicants of the present invention filed with the Japanese Patent Office on Nov. 18, 1985 as Japanese Patent Application No. 60-256703. In the above mentioned rotary nozzle, there is no possibility of molten steel leakage since the collector nozzle (14) is mounted to the rotor (8) in pouring, the annular support frame (6) is locked and fixed to the base member (2) with bolts, and both the bottom plate prior (3) and the slide plate brick (11) are tightly joined with each other by means of a repulsion of the coil spring (16), as seen in FIG. 4. If necessary, the pouring amount of molten steel can be controlled by rotating the rotor with a driving source and by adjusting an opening angle of the nozzles (4) and (16).
FIGS. 6 and 7 each are model diagrams explaining the mechanism of molten steel leakage in a prior art rotary nozzle. The rotary nozzle is mounted on the bottom portion of a ladle and injects molten steel into a molding machine, as described above. The edge portions of the nozzle (4) and (12) are melted and removed out in wedge shapes by high temperature molten steel (21) with a lapse of time. The molten steel enters and solidified in the wedge shape portions, as shown in FIG. 6(a). When the slide plate brick (11) is slide toward the arrow as shown in FIG. 6(b), the solidified molten steel remains without being smashed, and occurs a gap g between the sliding surfaces of both the bricks (3) and (11). This phenomenon is true even in the rotary nozzle. When the slide plate brick (11) is rotated to control pouring of molten steel as shown in FIG. 7, the solidified molten steel forcibly opens one end (near to the nozzle hole (12)) of the slide plate brick (11) against the coil spring (16) to form a gap g. In this case, the other end of the slide plate brick (11) works as a fulcram line a. As a result, the molten steel leaks through the gap g. This problem has required early repairs of the bricks (3) and (11) and early exchanges of expensive bottom plate bricks and slide plate bricks before an occurrence of the molten steel leakage. Elimination of these above mentioned disadvantages is a priority.
The object of the present invention is to provide an improved rotary nozzle which can prevent molten steel leakage out of the nozzle hole over a long period of time by removing a part of the coil springs.